Use of a coating composition to coat the backing film of a photovoltaic module, and photovoltaic module

Abstract

The invention relates to the use of a coating composition to coat the backing film of a photovoltaic module. The coating composition is a 2-component coating composition comprising a resin component (A) and a crosslinker component (B). The resin component (A) comprises a1) a polyester having a hydroxyl number of 60 to 300 mg KOH/g and a glass transition temperature T g of −65° C. to 50° C., a2) a poly(meth)acrylate (co)polymer having a hydroxyl number of 50 to 250 mg KOH/g and a glass transition temperature of −65° C. to 50° C., a3) pigments and/or fillers, a4) coating additives, a5) optionally a light stabilizer, a6) a phosphoric ester, and a7) organic solvent. The crosslinker component (B) comprises b1) a polyisocyanate and b2) optionally organic solvent. The invention also relates to a corresponding photovoltaic module.

1 : A method for coating the backing film of a photovoltaic module, the method comprising:
 coating a backing film with a coating composition to form a coating on the backing film,   wherein the coating composition is a 2-component coating composition comprising:
 a resin component (A); and 
 a crosslinker component (B), 
   the resin component (A) comprising:   a1) 3 to 20 wt %, based on the nonvolatile fraction of the resin component, of a polyester having a hydroxyl number of 60 to 300 mg KOH/g and a glass transition temperature T g  of −65° C. to 50° C.,   a2) 10 to 40 wt %, based on the nonvolatile fraction of the resin component, of a poly(meth)acrylate (co)polymer having a hydroxyl number of 50 to 250 mg KOH/g and a glass transition temperature of −65° C. to 50° C.,   a3) 40 to 86 wt %, based on the nonvolatile fraction of the resin component, of pigment and/or fillers a filler,   a4) 0.1 to 10 wt %, based on the nonvolatile fraction of the resin component, of a coating additives additive,   a5) 0 to 6 wt %, based on the nonvolatile fraction of the resin component, of a light stabilizer,   a6) 0.01 to 1 wt %, based on the nonvolatile fraction of the resin component, of phosphoric esters of the general formula
   PO (OR) n  (OH) m , 
   in which   n=1-3,   m=0-2, and   n+m=3,   R is selected from the group consisting of straight-chain or branched alkyl radicals having 1 to 16 carbon atoms, which may be substituted by aromatic radicals and/or may contain ether oxygen atoms (—O—), and aromatic radicals, which may be substituted by alkyl radicals having 1 to 6 carbon atoms,   the sum total of constituents a1) to a6) being 100 wt %, and   a7) 20 to 50 wt %, based on the total weight of the resin component (A), of organic solvent, and   
       the crosslinker component (B) comprising:
 b1) 30 to 100 wt % polyisocyanate, and 
 b2) 0 to 70 wt % of organic solvent, 
 the sum total of the constituents b1) and b2) being 100 wt %. 
 
     
     
         2 : The method as claimed in  claim 1 , wherein the organic solvent present in the resin component (A) and in the crosslinker component (B) is an acetate compound or an aromatic compound. 
     
     
         3 : The method as claimed in  claim 1 , wherein the backing film comprises at least one of polyethylene terephthalate, polyvinyl fluoride, and polyvinylidene fluoride. 
     
     
         4 : The method as claimed in  claim 1 , wherein the an outside of the backing film is coated. 
     
     
         5 : The method as claimed in  claim 1 , wherein the an outside and the an inside of the backing film are coated. 
     
     
         6 : The method as claimed in  claim 1 , wherein the a wet-film thickness of the coating is 10 to 40 μm. 
     
     
         7 : The method as claimed in  claim 1 , wherein said coating is carried out by spraying, by rolling, or knife coating the coating composition to the backing film. 
     
     
         8 : The method as claimed in  claim 1 , further comprising:
 curing the coating composition at a temperature of from 110° C. to 150° C. within a time period of 20 to 40 seconds.   
     
     
         9 : A photovoltaic module having comprising a coated backing film, wherein the coating of the coated backing film is a cured
 coating composition, wherein   the coating composition is a 2-component coating composition comprising:
 a resin component (A); and 
 a crosslinker component (B), 
   
       the resin component (A) comprising:
 a1) 3 to 20 wt %, based on the nonvolatile fraction of the resin component, of a polyester having a hydroxyl number of 60 to 300 mg KOH/g and a glass transition temperature T g  of −65° C. to 50° C., 
 a2) 10 to 40 wt %, based on the nonvolatile fraction of the resin component, of a poly(meth)acrylate (co)polymer having a hydroxyl number of 50 to 250 mg KOH/g and a glass transition temperature of −65° C. to 50° C., 
 a3) 40 to 86 wt %, based on the nonvolatile fraction of the resin component, of pigment and/or a filler, 
 a4) 0.1 to 10 wt %, based on the nonvolatile fraction of the resin component, of a coating additive, 
 a5) 0 to 6 wt %, based on the nonvolatile fraction of the resin component, of a light stabilizer, 
 a6) 0.01 to 1 wt %, based on the nonvolatile fraction of the resin component, of phosphoric esters of the general formula
   PO (OR) n  (OH) m , 
 
 
       in which
 n=1-3, 
 m=0-2, and 
 n+m=3, 
 R is selected from the group consisting of straight-chain or branched alkyl radicals having 1 to 16 carbon atoms, which may be substituted by aromatic radicals and/or may contain ether oxygen atoms (—O—), and aromatic radicals, which may be substituted by alkyl radicals having 1 to 6 carbon atoms, the sum total of constituents a1) to a6) being 100 wt %, and 
 a7) 20 to 50 wt %, based on the total weight of the resin component (A), of organic solvent, and 
 the crosslinker component (B) comprising: 
 b1) 30 to 100 wt % polyisocyanate; and 
 b2) 0 to 70 wt % of organic solvent, the sum total of the constituents b 1) and b2) being 100 wt %. 
 
     
     
         10 : The photovoltaic module as claimed in  claim 9 , wherein the backing film comprises at least one of polyethylene terephthalate, polyvinyl fluoride, or polyvinylidene fluoride. 
     
     
         11 : The photovoltaic module as claimed in  claim 9 , wherein an outside of the backing film is coated. 
     
     
         12 : The photovoltaic module as claimed in  claim 9 , wherein an outside and an inside of the backing film are coated. 
     
     
         13 : The photovoltaic module as claimed in  claim 9 , wherein a dry-film thickness of the coating is 20 to 35 μm.